Characterization of a bioactive polysaccharide from Ganoderma atrum: Re-elucidation of the fine structure

• Published in: Carbohydrate polymers Vol. 158; pp. 58 - 67
• Main Authors: Zhang, Hui, Nie, Shaoping, Cui, Steve W., Xu, Ming, Ding, Huihuang, Xie, Mingyong
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 20.02.2017
• Subjects: Chromatography, Liquid; Fine structure; Fungal Polysaccharides - chemistry; Ganoderma - chemistry; Ganoderma atrum; Hydrolysis; Magnetic Resonance Spectroscopy; Mass Spectrometry; Methylation; Monosaccharides; NMR spectroscopy; Partial acid hydrolysis; Polysaccharide; Fine structure; Ganoderma atrum; Methylation; NMR spectroscopy; Polysaccharide; Partial acid hydrolysis
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2016.11.088

•PSG-1 was re-purified and the structure was re-elucidated with more evidences.•β-(1→3)-glucan was identified as the backbone with branch point at O-6 of glucose.•Long β-(1→6)-glucose side chain was proposed.•β-(1→4)-GlcA was found in the side chain of PSG-1. The fine structure in terms of backbone and branch chain features of a bioactive polysaccharide from Ganoderma atrum (PSG-1) was re-elucidated systematically using high performance anion-exchange chromatography (HPAEC), methylation and GLC–MS analysis, and 1D & 2D NMR spectroscopy. Monosaccharide composition analysis revealed that PSG-1-F0.2 fraction mainly consisted of glucose (73.8%) and glucuronic acid (15.3%), with small amount of mannose (5.7%) and galactose (5.2%). Based on methylation, multistep partial acid hydrolysis and NMR study, ▪ were proposed to substitute at the O-6 position of β-(1→3)-glucan. The small amount of mannose and galactose residues were considered to be from the other fraction in PSG which was very difficult to be separated from PSG-1-F0.2. This revised structure as an acidic β-(1→3, 1→6)-glucan is considered to be more accurate than the previous proposal of PSG-1.